1. Field of the Invention
The present invention relates to a laser processing method that uses a laser beam for the structural formation of a work piece, and also, relates to a laser processing apparatus therefor.
Further, the invention relates to a laser processing method and a laser processing apparatus preferably suitable for micro-processing of materials used for a micromachine, or ICs and diode devices, among some others.
2. Related Background Art
Conventionally, as means for processing a minute three-dimensional structure of a submicron to 10 micron order, it has usually been practiced to use a lithographic process. For such a process, a method has been adopted for processing a structure through a series of etching, resist ashing, and others that utilize resist coating, resist patterning exposure, resist development, and resist patterns.
However, for the lithographic process described above which is used for processing a minute three-dimensional structure of a submicron to 10 micron order, the processing steps become complicated so as to create not only a problem related to costs against tact-time, but also, a problem of an enormous amount of investment in constructing production facilities. Then, furthermore, it is extremely difficult for the lithographic process to form a structure having a high aspect ratio.
The present invention is designed with a view towards solving the problems discussed above, and is aimed at the provision of laser processing methods, as well as a laser processing apparatus, to provide simple and easy processing steps in which a three-dimensional micro-structure is processed without using any complicated processing steps such as lithographic processing steps.
In order to achieve the objectives, the laser processing methods of the present invention are provided as given in the following paragraphs (1) to (19), and a laser processing apparatus in (20) to (24):
(1) A laser processing method, which uses a laser beam from a laser oscillator to emit, continuously, a light pulse having a large spacial and temporal energy concentration in a pulse emission period of one picosecond or less, and projects a mask pattern with a projection lens onto a work piece almost transparent to the wavelength of the laser beam for sublimation processing thereof, comprises the following steps of: setting the focal point of projecting an image of the mask pattern on the surface of a contour boundary of the opposite side of the work piece irradiated by the laser when the processing begins, and irradiating and converging the laser beam on the focal point portion so as to make the energy concentration thereof to be more than a threshold value enabling a designated ablative action to be generated; moving the work piece in the direction of laser irradiation gradually in a designated amount or at a designated speed in synchronism with the progress of ablation processing by the irradiation of the laser beam; and forming a structure on the work piece in the form of being inserted into and drawn from the contour boundary surface on the opposite side of the laser irradiation to the side of the laser irradiation.
(2) In the laser processing method referred to in paragraph (1), when a structure is processed in the interior of a work piece by performing sublimation processing, the structure is processed after a releasing outlet is formed in advance to release, externally, a substance produced by sublimate evaporation of the processing of the work piece.
(3) In the laser processing method referred to in paragraph (2), when the structure is processed, processing begins with the position of the structure being in contact with the releasing outlet.
(4) In the laser processing method referred to in paragraph (1), the laser oscillator is a laser oscillator provided with a space compression device for light propagation.
(5) In the laser processing method referred to in paragraph (4), the space compression device for light propagation comprises means for generating chirped pulses, and means for synchronizing a vertical mode utilizing a dispersion characteristic of the light wavelength.
(6) In the laser processing method referred to in paragraph (1), at the same time as the laser irradiation, processing is performed, while the mask pattern is dynamically changed in synchronism with the progress of the light ablation processing.
(7) In the laser processing method referred to in paragraph (6), means for dynamically changing the mask pattern is the light transmission mask of a liquid crystal device capable of controlling patterns dynamically.
(8) In the laser processing method referred to in paragraph (7), a laser beam incident upon the mask is linearly polarized light, and the polarization filter used for the liquid crystal device comprises only a single sheet light emission polarization filter vertical or horizontal to the polarizing direction of the incident laser beam corresponding to the setting of negative or positive transmission.
(9) A laser processing method, which uses a laser beam from a laser oscillator to emit, continuously, a light pulse having a large special and temporal energy concentration in a pulse emission period of one picosecond or less, and projects a mask pattern onto a work piece with a projection lens for the processing thereof, comprises the step of processing the work piece by changing the mask pattern dynamically in synchronism with the progress of processing the work piece by the use of a laser beam.
(10) In the laser processing method referred to in paragraph (9), the mask is the light transmission mask of a liquid crystal device capable of controlling patterns dynamically.
(11) In the laser processing method referred to in paragraph (9), a laser beam incident upon the mask is linearly polarized light, and the polarization filter used for the liquid crystal device comprises only a single sheet light emission polarization filter vertical or horizontal to the polarizing direction of the incident laser beam corresponding to the setting of negative or positive transmission.
(12) In the laser processing method referred to in paragraph (9), the focal point of the projected mask pattern image is focused on the processing position in the direction of an optical axis in synchronism with the progress of processing the work piece so as to displace the position of a mask or work piece to follow.
(13) In the laser processing method referred to in paragraph (9), the laser oscillator is a laser oscillator provided with a space compression device for light propagation.
(14) In the laser processing method referred to in paragraph (9), the space compression device for light propagation comprises means for generating chirped pulses, and means for synchronizing a vertical mode utilizing a dispersion characteristic of the light wavelength.
(15) A laser processing method, which uses a laser beam irradiated from a laser oscillator to emit, continuously, a light pulse having a large spacial and temporal energy concentration in a pulse emission period of one picosecond or less, comprises the following step of irradiating a laser beam onto a work piece having a multiply layered structure having different absorption characteristics of the laser beam wavelength; and processing the work piece with a designated pattern and designated energy concentration.
(16) In the laser processing method referred to in paragraph (15), the work piece having a multiply layered structure is a plate or structural body being semi-transparent tot he light wavelength of the laser beam, and formed by laminating or bonding a plurality of materials each having different light absorption characteristics.
(17) In the laser processing method referred to in paragraph (15), the light intensity distribution of the light pulse is a Gaussian beam.
(18) In the laser processing method referred to in paragraph (15), the laser oscillator is a laser oscillator provided with a space compression device for light propagation.
(19) In the laser processing method referred to in paragraph (18), the space compression device for light propagation comprises means for generating chirped pulses, and means for synchronizing a vertical mode utilizing a light dispersion characteristic of the light wavelength.
(20) A laser processing apparatus, which uses a laser beam from a laser oscillator to emit, continuously, a light pulse having a large spacial and temporal energy concentration in a pulse emission period of one picosecond or less, and projects a mask pattern onto a work piece with a projection lens for the processing thereof, comprises means for changing the mask pattern dynamically in synchronism with the progress of processing the work piece by the use of a laser beam.
(21) I the laser processing apparatus referred to in paragraph (20), the means for changing a mask pattern dynamically is a light transmission mask capable of controlling a pattern dynamically by use of a liquid crystal device.
(22) In the laser processing apparatus referred to in paragraph (21), a laser beam incident upon the mask is linearly polarized light, and the polarization filter used for the liquid crystal device comprises only a single sheet light emission polarization filter vertical or horizontal to the polarizing direction of the incident laser beam corresponding to the setting o negative or positive transmission.
(23) In the laser processing apparatus referred to in paragraph (21), the laser oscillator is a laser oscillator provided with a space compression device for light propagation.
(24) In the laser processing apparatus referred to in paragraph (23), the space compression device for light propagation comprises means for generating chirped pulses, and means for synchronizing a vertical mode utilizing a light dispersion characteristic of the light wavelength.